Method of making a lead cable assembly



1964 R. B. MOLAUGHLIN ETAL 3,

METHOD OF MAKING A LEAD CABLE ASSEMBLY Filed June 23, 1960 INVENTOR. Ronald R. Sinclair and RUssel/ B. McLauyh/m m wfw United States Patent M 3,152,028 METHUD OF lVIAKING A LEAD CABLE ASSEMBLY Russell B. McLaughlin and Ronald R. Sinclair, Lancaster, Pa., assignors to AMP Incorporated, Harrisburg, Pa. Filed June 23, 1960, Ser. No. 38,368 3 Claims. (Cl. 156-48) The use of electrical conductors at high altitudes and high voltage presents special problems. Not the least of these is the effect of corona-discharge which is an arcing of the conductor caused by the high voltage and the low dielectric strength of the atmosphere at high altitudes. This phenomenon is responsible for power loss in the circuit. One way to prevent corona-discharge "is to insulate the conductor such as by molding an insulation around the outside of the conductor. The disadvantage of this solution is that during assembly and use the surface of the conductor works itself away from the inner surface of the molded insulation thus creating air pockets. These air pockets then set up areas of corona-discharge.

Stranded wire is particularly vulnerable in this respect. This is because the inner surface of the insulation conforms to the lay of the stranded conductor. When the outer surface of the conductor becomes displaced from its conforming inner surface of insulation, the voids forming air pockets are more pronounced.

It is an object of this invention to provide an electrical cable which is corona free at extremely high voltages. It is also an object of this invention to provide a method of making such a cable with the insulation filled with a silicone grease.

Other objects and attainments of the present invention will become apparent to those skilled in the art upon a reading of the following detailed description when taken in conjunction with the drawings in which there is shown and described an illustrative embodiment of the invention; it is to be understood, however, that this embodiment is not intended to be exhaustive nor limiting of the invention but is given for purposes of illustration in order that others skilled in the art may fully understand the invention and the principles thereof and the manner of applying it in practical use so that they may modify it in various forms, each as may be best suited to the conditions of a particular use.

FIGURE 1 is a sectional view of a cable connector.

FIGURE 2 is a perspective view illustrating an insulating sleeve being filled with high dielectrical, unctuous material and the conductive core removed.

FIGURE 3 is a perspective view showing the conductive core being reinserted into the insulation sleeve.

FIGURE 4 is a view of the device embodying the principles of this invention in final, assembled form.

FIGURE 5 is a sectional view illustrating the cable of FIGURE 1.

FIGURE 6 is a view similar to FIGURE 5 showing the conductor having worked its way away from the insulation to provide air pockets between the conductor and the insulation.

FIGURE 7 is a view similar to FIGURE 6 showing the pockets between the conductor and the insulation filled with silicone grease.

As shown in the drawing, FIGURE 1, the insulated conductor generally indicated by the letter A comprises a central core which is a metallic stranded conductor it), completely surrounded by an insulating material, eg silicone rubber. As shown in FIGURE 5, molding the silicone rubber about the conductor causes the inner surface of the insulation to assume the shape of the outer surface of the conductor. The braided stranded conductor forms a plurality of crests and troughs with the insulation forming complementary crests and troughs.

3,152,028 F atented Oct. 6, 1964 The crest of the conductor opposes the trough of the insulation and the trough of the conductor opposes the crest of the insulation.

In usage when an insulated cable is flexed, or otherwise disturbed, the conductor works free from the insulation so that the area forming a trough on the conductor may realign itself with an area forming a trough on the insulation. This forms a void which permits corona-discharge, when a high voltage is passed through the conductor.

As shown in FIGURE 7, filling the air pockets with an unctuous material 14-, having high dielectrical strength such as a silicone grease, seals off these air pockets, provides a good dielectric insulation, and effectively precents corona-discharge.

To fill these voids with grease, it is desirable that the central conductor be entirely removed from the cen ter of the insulation (see FIGURE 2). A grease gun filled with the unctuous material is disposed with its nozzle inserted centrally of the insulation sleeve and the grease is discharged into the insulating cover.

In the meantime a receptacle 18 (FIGURE 2) may be applied to the conductor and the unctuous material applied to the receptacle 1%. A lead wire 22, which is finer than the cable It), is applied to the opposite end thereof. The lead wire 22 is then fed through the insulating jacket 1?; until it emerges from the other end thereof pulling the cable It behind it. The lead 22 is threaded through the core of the cable 12 until the conductor is properly positioned within the insulation sleeve with the receptacle 18 inserted in one end thereof. Suitable caps are placed over each end of the insulating sleeve to prevent discharge of silicone grease. As noted in FIGURE 7 the grease fills the interstices between the stranded cable 18 and the inner surface of the molded silicone 12.

It has been observed that untreated silicone covered cable which is capable of generating corona at 7,500 volts has been improved by this method to a degree wherein it is capable of withstanding 14,000 volts without developing any corona-discharge.

Changes in construction will occur to those skilled in the art and various apparently different modifications and embodiments may be made without departing from the scope of the invention. The matter set forth in the foregoing description and accompanying drawings is ofiered by way of illustration only. The actual scope of the invention is intended to be defined in the following claims when viewed in their proper perspective against the prior art.

We claim:

1. The method of making an insulating electrical cable capable of carrying high voltages without corona discharge from a length of flexible electrical cable having an outer sleeve of insulating material and a central stranded conductor including the steps of (I) withdrawing the central conductor from the insulating sleeve to provide a central bore, (2) filling the bore with an unctuors material having a high dielectric strength, and (3) threading the central conductor through the bore within the insulating sleeve.

2. The method of making a high voltage conductor assembly utilizing flexible electrical cable having an insulation sleeve surrounding a central conductor which includes the steps of: (1) removing the conductor from the insulation sleeve, (2) filling the insulation sleeve with a substance capable of protecting the conductor against corona-discharge, (3) inserting said conductor back into said sleeve ,(4) applying means for preventing escape of the material for preventing high voltage discharge.

3. A method of making a high voltage lead assembly utilizing electrical cable having an insulation sleeve which includes the steps of: (1) filling the insulating sleeve with a silicone grease, (2) securing a threading device onto a conductor, (3) inserting said threading device into the insulating sleeve so that it pulls the conductor after it, and positions said conductor centrally of the sleeve, (4) sealing the ends of the sleeve against the extrusion of the silicone grease.

References Cited in the file of this patent UNITED STATES PATENTS Warner Apr. 6, Keyes Apr. 18, Elliott et al. May 16, Redslob Dec. 3, Lorch et al. Aug. 9, Grieve May 1, 

1. THE METHOD OF MAKING AN INSULATING ELECTRICAL CABLE CAPABLE OF CARRYING HIGH VOLTAGES WITHOUT CORONA DISCHARGE FROM A LENGTH OF FLEXIBLE ELECTRICAL CABLE HAVING AN OUTER SLEEVE OF INSULATING MATERIAL AND A CENTRAL STRANDED CONDUCTOR INCLUDING THE STEPS OF (1) WITHDRAWING THE CENTRAL CONDUCTOR FROM THE INSULATING SLEEVE TO PROVIDE A CENTRAL BORE, (2) FILLING THE BORE WITH AN UNCTUORS MATERIAL HAVING A HIGH DIELECTRIC STRENGTH, AND (3) THREADING THE CENTRAL CONDUCTOR THROUGH THE BORE WITHIN THE INSULATING SLEEVE. 